5 replies to this topic

[Nevyn]

I am trying to talk to 2 I2C devices on the same I2C bus, one is a TMP102 temperature sensor on address 0x48 and the other is a STM8S set up as an I2C slave with address 0x50.

 

I know that I can talk to both of these independently but what I'm looking to do is to try and have the two devices on the same bus but I am getting an error.

 

My code looks like this:

using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using System.Threading;

namespace I2CMaster
{
    public class Program
    {
        public static void Main()
        {
            I2CDevice i2cBus = new I2CDevice(new I2CDevice.Configuration(0x50, 50));
            I2CDevice tmp102 = new I2CDevice(new I2CDevice.Configuration(0x48, 50));
        }
    }
}

The second statement generates an exception:

 

An unhandled exception of type 'System.InvalidOperationException' occurred in Microsoft.SPOT.Hardware.dll

 

What I do not know is if this is expected behaviour, i.e. am I supposed to setup one I2C device, do some stuff with it and then release the I2C device before moving on to the second one.

 

Anyone out there reading from two I2C slaves on the same bus with NETMF ?

 

Regards,

Mark

[Nevyn]

Bit of alternative thinking and I got the solution.

 

Set up the I2C bus as follows:

I2CDevice.Configuration stm8s = new I2CDevice.Configuration(0x50, 50);
I2CDevice.Configuration tmp102 = new I2CDevice.Configuration(0x48, 50);
I2CDevice i2cBus = new I2CDevice(stm8s);

Then when you want to read from the different devices just change the config:

i2cBus.Config = stm8s;
int bytesRead = i2cBus.Execute(transactions, 100);
i2cBus.Config = tmp102;
bytesRead = i2cBus.Execute(reading, 100);

Not sure if that's how it supposed to work but I get the right results.

 

Regards,

Mark

[Frode]

Mark, somewhere on the forum is an I2CBus class which will allow you to use multiple I2C devices. Search for I2CBus.cs or similar.

[Frode]

Here it is: http://forums.netdui...cbus/#entry4156

[Nevyn]

Here it is: http://forums.netdui...cbus/#entry4156

Thanks for the pointers.

 

If you are interested in what I was doing then there's more information here:

Creating I2C master devices with the STM8S

Creating I2C slave devices using the STM8S

 

The Netduino 3 allowed me to have a known working reference for the I2C protocol.

 

Regards,

Mark

[Frode]

Nice - I've also written a TMP102 driver for Netduino (https://github.com/S...ature/TMP102.cs).